Wang, Jia-WeiLai, Shih-PingEswaraiah, ChakaliClemens, Dan P.Chen, Wen-PingPandey, Anil K.2018-02-202018-02-202017-11-10Jia-Wei Wang, Shih-Ping Lai, Chakali Eswaraiah, Dan P Clemens, Wen-Ping Chen, Anil K Pandey. 2017. "Multiwavelength Stellar Polarimetry of the Filamentary Cloud IC5146. I. Dust Properties." ASTROPHYSICAL JOURNAL, Volume 849, Issue 2:157 (18pp).0004-637X1538-4357https://hdl.handle.net/2144/27092We present optical and near-infrared stellar polarization observations toward the dark filamentary clouds associated with IC5146. The data allow us to investigate the dust properties (this paper) and the magnetic field structure (Paper II). A total of 2022 background stars were detected in the Rc, i¢, H, and/or K bands to AV  25 mag. The ratio of the polarization percentage at different wavelengths provides an estimate of lmax, the wavelength of the peak polarization, which is an indicator of the small-size cutoff of the grain size distribution. The grain size distribution seems to significantly change at AV ~ 3 mag, where both the average and dispersion of P P R H c decrease. In addition, we found lmax ~ 0.6 0.9 – μm for AV > 2.5 mag, which is larger than the ∼0.55 μm in the general interstellar medium (ISM), suggesting that grain growth has already started in low-AV regions. Our data also reveal that polarization efficiency (PE º P A l V ) decreases with AV as a power law in the Rc, i¢, and K bands with indices of −0.71 ± 0.10, −1.23 ± 0.10, and −0.53 ± 0.09. However, H-band data show a power index change; the PE varies with AV steeply (index of −0.95 ± 0.30) when AV <  2.88 0.67 mag, but softly (index of −0.25 ± 0.06) for greater AV values. The soft decay of PE in high-AV regions is consistent with the radiative alignment torque model, suggesting that our data trace the magnetic field to AV ~ 20 mag. Furthermore, the breakpoint found in the H band is similar to that for AV, where we found the P P R H c dispersion significantly decreased. Therefore, the flat PE–AV in high-AV regions implies that the power-index changes result from additional grain growth.18ppScience & technologyPhysical sciencesAstronomy & astrophysicsDust, extinctionISM: cloudsISM: individual objects (IC5146)ISM: magnetic fieldsISM: structurePolarizationInterstellar linear polarizationGrain alignmentWavelength dependenceIC 5146Astronomical and space sciencesOrganic chemistryPhysical chemistry (incl. Structural)Astronomy & astrophysicsArticle10.3847/1538-4357/aa937f0000-0002-9947-4956 (Clemens, Dan P)